1. Technical Field
The present invention relates to a touch detection field and, particularly to a liquid crystal display device with touch function and a touch panel.
2. Description of the Related Art
With the rapid development of science and technology, since flat panel display devices such as, liquid crystal display devices have many advantages of high image quality, small volume, lightweight and wide application-range, etc., and thus are widely applied into various consumer electronics products such as mobile phones, notebook computers, desktop display devices and televisions, etc. Moreover, the liquid crystal display devices have evolved into a mainstream display device in place of traditional cathode ray tube (CRT) display devices.
A touch panel provides a new human-machine interface and is more intuitional and more suitable for human nature in use. If the touch panel is integrated with a liquid crystal display device together, the liquid crystal display device then is endowed with touch function and has been become a development and application trend of the liquid crystal display device.
Referring to FIG. 1, showing a schematic circuit diagram of a conventional sensing/detection unit adapted into a liquid crystal display device with touch function. It is well-known that the liquid crystal display device generally includes two substrates and a liquid crystal layer sandwiched between the two substrates. One of the substrates has a plurality of scan lines and a plurality of data lines disposed on. The scan lines and the data lines are arranged crossing with each other and whereby dividing the liquid crystal display device into a plurality of pixel regions. For making the liquid crystal display device have the touch function, the liquid crystal display device further includes a plurality of sensing units which are respectively disposed in some of the pixel regions.
As shown in FIG. 1, the conventional sensing unit 10 adapted into the liquid crystal display device with the touch function generally includes three transistors and two capacitors (3T2C structure), and those are a transistor 11, a transistor 12, a transistor 13, a reference capacitor 15 and a liquid crystal capacitor 16. A gate electrode of the transistor 11 is electrically coupled to a corresponding scan line Gn, and a source electrode of the transistor 11 is electrically coupled to an external power source Vinit. A gate electrode of the transistor 12 is electrically coupled to a drain electrode of the transistor 11, and a source electrode of the transistor 12 is electrically coupled to the external power source Vinit. A gate electrode of the transistor 13 is electrically coupled to a next scan line Gn+1 adjacent to the corresponding scan line Gn, a source electrode of the transistor 13 is electrically coupled to a drain electrode of the transistor 12, and a drain electrode of the transistor 13 is electrically coupled to a corresponding readout line Rn. The reference capacitor 15 is electrically coupled between the corresponding scan line Gn and the drain electrode of the transistor 11, and the liquid crystal capacitor 16 is electrically coupled between the drain electrode of the transistor 11 and a common potential Vcom. It is understood to the skilled person in the art that, the liquid crystal capacitor 16 is formed by a pixel electrode, a common electrode and a liquid crystal layer sandwiched therebetween, and thus the liquid crystal capacitor 16 has a capacitance value altered in compliance with the pressed degree of the sensing unit 10.
Since the conventional sensing unit 10 necessarily needs three transistors and two capacitors and is disposed in the pixel region, a large size of the sensing unit 10 inevitably would influence the aperture ratio of the liquid crystal display device. In addition, since each of the transistors consumes a certain cross-voltage and forms a certain parasitic capacitance, excessive amount of transistors would result in the sensing unit 10 having a small range output voltage, and the excessive amount of parasitic capacitances would cause signal attenuation.